基于列标签的CachedRowSetImpl getString会抛出“无效列名”。

时尚小姥姥

当我执行以下代码时，一切都很好：
ResultSet rs = con.prepareStatement("SELECT r.UID AS R FROM r").executeQuery();
System.out.println(rs.getMetaData().getColumnLabel(1));
rs.next();
System.out.println(rs.getString("R"));
结果是：
R
23
但是当我执行以下代码时：
ResultSet rs = con.prepareStatement("SELECT r.UID AS R FROM r").executeQuery();
CachedRowSetImpl rslt = new CachedRowSetImpl();
rslt.populate(rs);
System.out.println(rslt.getMetaData().getColumnLabel(1));
rslt.next();
System.out.println(rslt.getString("R"));
结果是：
R
java.sql.SQLException: Invalid column name
为什么在这里抛出异常？

解决方案:


            问题是，参考实现CachedRowSet（com.sun.rowset.CachedRowSetImpl）包含一个错误：当您通过名称检索列，它使用的columnName，而
不是
在columnLabel，为此逆着它使用JDBC规范的其余部分columnLabel检索值。此错误使得不可能通过来从行集中检索值columnLabel。
Oracle的错误是http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7046875，但是（感到惊讶）他们使该错误无法供公众查看。
有两种可能的解决方法。一种是检查驱动程序是否提供了一个属性，以使该ResultSetMetaData.getColumnName(..)方法也返回该columnLabel值，第二种解决方法是创建的子类CachedRowSetImpl（不幸的是，它需要很多重写方法）。
以下版本是从此消息复制的：http : //tech.groups.yahoo.com/group/Firebird-
Java/message/10715
import java.math.BigDecimal;
import java.sql.Array;
import java.sql.Blob;
import java.sql.Clob;
import java.sql.Ref;
import java.sql.SQLException;
import java.util.Calendar;
import java.util.Collection;
import java.util.Hashtable;
import javax.sql.rowset.RowSetMetaDataImpl;
import com.sun.rowset.CachedRowSetImpl;
public class FixedCachedRowSetImpl extends CachedRowSetImpl {
private static final long serialVersionUID = -9067504047398250113L;
private RowSetMetaDataImpl RowSetMD;
public FixedCachedRowSetImpl() throws SQLException {
      super();
}
public FixedCachedRowSetImpl(Hashtable env) throws SQLException {
      super(env);
}
private int getColIdxByName(String name) throws SQLException {
      RowSetMD = (RowSetMetaDataImpl) this.getMetaData();
      int cols = RowSetMD.getColumnCount();
      for (int i = 1; i  toCollection(String column) throws SQLException {
      return toCollection(getColIdxByName(column));
}
@Override
public String getString(String columnName) throws SQLException {
      return getString(getColIdxByName(columnName));
}
@Override
public boolean getBoolean(String columnName) throws SQLException {
      return getBoolean(getColIdxByName(columnName));
}
@Override
public byte getByte(String columnName) throws SQLException {
      return getByte(getColIdxByName(columnName));
}
@Override
public short getShort(String columnName) throws SQLException {
      return getShort(getColIdxByName(columnName));
}
@Override
public int getInt(String columnName) throws SQLException {
      return getInt(getColIdxByName(columnName));
}
@Override
public long getLong(String columnName) throws SQLException {
      return getLong(getColIdxByName(columnName));
}
@Override
public float getFloat(String columnName) throws SQLException {
      return getFloat(getColIdxByName(columnName));
}
@Override
public double getDouble(String columnName) throws SQLException {
      return getDouble(getColIdxByName(columnName));
}
@Override
public BigDecimal getBigDecimal(String columnName, int scale) throws SQLException {
      return getBigDecimal(getColIdxByName(columnName), scale);
}
@Override
public byte[] getBytes(String columnName) throws SQLException {
      return getBytes(getColIdxByName(columnName));
}
@Override
public java.sql.Date getDate(String columnName) throws SQLException {
      return getDate(getColIdxByName(columnName));
}
@Override
public java.sql.Time getTime(String columnName) throws SQLException {
      return getTime(getColIdxByName(columnName));
}
@Override
public java.sql.Timestamp getTimestamp(String columnName) throws SQLException {
      return getTimestamp(getColIdxByName(columnName));
}
@Override
public java.io.InputStream getAsciiStream(String columnName) throws SQLException {
      return getAsciiStream(getColIdxByName(columnName));
}
@Override
public java.io.InputStream getUnicodeStream(String columnName) throws SQLException {
      return getUnicodeStream(getColIdxByName(columnName));
}
@Override
public java.io.InputStream getBinaryStream(String columnName) throws SQLException {
      return getBinaryStream(getColIdxByName(columnName));
}
@Override
public Object getObject(String columnName) throws SQLException {
      return getObject(getColIdxByName(columnName));
}
@Override
public int findColumn(String columnName) throws SQLException {
      return getColIdxByName(columnName);
}
@Override
public java.io.Reader getCharacterStream(String columnName) throws SQLException {
      return getCharacterStream(getColIdxByName(columnName));
}
@Override
public BigDecimal getBigDecimal(String columnName) throws SQLException {
      return getBigDecimal(getColIdxByName(columnName));
}
@Override
public boolean columnUpdated(String columnName) throws SQLException {
      return columnUpdated(getColIdxByName(columnName));
}
@Override
public void updateNull(String columnName) throws SQLException {
      updateNull(getColIdxByName(columnName));
}
@Override
public void updateBoolean(String columnName, boolean x) throws SQLException {
      updateBoolean(getColIdxByName(columnName), x);
}
@Override
public void updateByte(String columnName, byte x) throws SQLException {
      updateByte(getColIdxByName(columnName), x);
}
@Override
public void updateShort(String columnName, short x) throws SQLException {
      updateShort(getColIdxByName(columnName), x);
}
@Override
public void updateInt(String columnName, int x) throws SQLException {
      updateInt(getColIdxByName(columnName), x);
}
@Override
public void updateLong(String columnName, long x) throws SQLException {
      updateLong(getColIdxByName(columnName), x);
}
@Override
public void updateFloat(String columnName, float x) throws SQLException {
      updateFloat(getColIdxByName(columnName), x);
}
@Override
public void updateDouble(String columnName, double x) throws SQLException {
      updateDouble(getColIdxByName(columnName), x);
}
@Override
public void updateBigDecimal(String columnName, BigDecimal x) throws SQLException {
      updateBigDecimal(getColIdxByName(columnName), x);
}
@Override
public void updateString(String columnName, String x) throws SQLException {
      updateString(getColIdxByName(columnName), x);
}
@Override
public void updateBytes(String columnName, byte x[]) throws SQLException {
      updateBytes(getColIdxByName(columnName), x);
}
@Override
public void updateDate(String columnName, java.sql.Date x) throws SQLException {
      updateDate(getColIdxByName(columnName), x);
}
@Override
public void updateTime(String columnName, java.sql.Time x) throws SQLException {
      updateTime(getColIdxByName(columnName), x);
}
@Override
public void updateTimestamp(String columnName, java.sql.Timestamp x) throws SQLException {
      updateTimestamp(getColIdxByName(columnName), x);
}
@Override
public void updateAsciiStream(String columnName, java.io.InputStream x, int length) throws SQLException {
      updateAsciiStream(getColIdxByName(columnName), x, length);
}
@Override
public void updateBinaryStream(String columnName, java.io.InputStream x, int length) throws SQLException {
      updateBinaryStream(getColIdxByName(columnName), x, length);
}
@Override
public void updateCharacterStream(String columnName, java.io.Reader reader, int length) throws SQLException {
      updateCharacterStream(getColIdxByName(columnName), reader, length);
}
@Override
public void updateObject(String columnName, Object x, int scale) throws SQLException {
      updateObject(getColIdxByName(columnName), x, scale);
}
@Override
public void updateObject(String columnName, Object x) throws SQLException {
      updateObject(getColIdxByName(columnName), x);
}
@Override
public Object getObject(String columnName, java.util.Map> map) throws SQLException {
      return getObject(getColIdxByName(columnName), map);
}
@Override
public Ref getRef(String colName) throws SQLException {
      return getRef(getColIdxByName(colName));
}
@Override
public Blob getBlob(String colName) throws SQLException {
      return getBlob(getColIdxByName(colName));
}
@Override
public Clob getClob(String colName) throws SQLException {
      return getClob(getColIdxByName(colName));
}
@Override
public Array getArray(String colName) throws SQLException {
      return getArray(getColIdxByName(colName));
}
@Override
public java.sql.Date getDate(String columnName, Calendar cal) throws SQLException {
      return getDate(getColIdxByName(columnName), cal);
}
@Override
public java.sql.Time getTime(String columnName, Calendar cal) throws SQLException {
      return getTime(getColIdxByName(columnName), cal);
}
@Override
public java.sql.Timestamp getTimestamp(String columnName, Calendar cal) throws SQLException {
      return getTimestamp(getColIdxByName(columnName), cal);
}
@Override
public void updateRef(String columnName, java.sql.Ref ref) throws SQLException {
      updateRef(getColIdxByName(columnName), ref);
}
@Override
public void updateClob(String columnName, Clob c) throws SQLException {
      updateClob(getColIdxByName(columnName), c);
}
@Override
public void updateBlob(String columnName, Blob b) throws SQLException {
      updateBlob(getColIdxByName(columnName), b);
}
@Override
public void updateArray(String columnName, Array a) throws SQLException {
      updateArray(getColIdxByName(columnName), a);
}
@Override
public java.net.URL getURL(String columnName) throws SQLException {
      return getURL(getColIdxByName(columnName));
}
}
您还可以查看org.springframework.jdbc.support.rowset.ResultSetWrappingSqlRowSet，其中还说：

注意：从JDBC
4.0开始，已经阐明，任何使用String来标识列的方法都应使用列标签。列标签是使用SQL查询字符串中的ALIAS关键字分配的。当查询不使用ALIAS时，默认标签为列名。大多数JDBC
ResultSet实现都遵循这种新模式，但是有一些例外，例如com.sun.rowset.CachedRowSetImpl类仅使用列名，而忽略任何列标签。从Spring
3.0.5开始，ResultSetWrappingSqlRowSet它将列标签转换为正确的列索引，以更好地支持，com.sun.rowset.CachedRowSetImpl这是使用JdbcTemplateRowSet时使用的默认实现。

基于列标签的CachedRowSetImpl getString会抛出“无效列名”。

时尚小姥姥 LV1